Circuit interconnect for optoelectronic device

ABSTRACT

This disclosure concerns systems and devices configured to implement impedance matching schemes in a high speed data transmission environment. In one example, an optoelectronic assembly is provided that includes a TO package having a base through which one or more leads pass. The leads are electrically coupled to an optoelectronic device in the TO package, and are electrically isolated from the base. Some or all of the leads include a ground ring that is electrically isolated from the lead and electrically coupled with the base. A circuit interconnect is also included that is electrically coupled to the optoelectronic device and the TO package. The circuit interconnect includes a dielectric substrate having signal traces that are electrically coupled to the signal leads. A ground signal conductor disposed on the dielectric substrate is electrically coupled with the ground rings.

The present invention relates generally to optoelectronic devices, andparticularly to a circuit interconnect for controlled impedance at highfrequencies.

BACKGROUND OF THE INVENTION

An optoelectronic device, such as a laser diode or a photo diode, isgenerally enclosed in a transistor outline (TO) package, which providesa conductive housing for the optoelectronic device. A laser diodeconverts an electrical signal into an optical signal for transmissionover a fiber optic cable, while a photo diode converts an optical signalinto an electrical signal. In order for a laser diode to convert anelectrical signal into an optical signal, the electrical signal must besent through the TO package of the laser diode. Similarly, an electricalsignal from a photo diode must be sent through the TO package of thephoto diode to external electrical circuitry. For high frequencyoperation, it is important to control the impedance seen by theelectrical signals that flow into and out of the TO package.

Conventional signal and ground connections to TO packages, whichincluding distinct signal and ground connections, result in uncontrolledimpedances that degrade data signal integrity at high frequencies (e.g.,at or above 3 GHz).

BRIEF SUMMARY OF AN EXEMPLARY EMBODIMENT OF THE INVENTION

In general, exemplary embodiments of the invention are concerned withsystems and devices configured to implement impedance matching schemesin a high speed data transmission environment. In one example, anoptoelectronic assembly is provided that includes a TO package having abase through which one or more leads pass. The leads are electricallycoupled to an optoelectronic device in the TO package, and areelectrically isolated from the base. Some or all of the leads include aground ring that is electrically isolated from the lead and electricallycoupled with the base. A circuit interconnect is also included that iselectrically coupled to the optoelectronic device and the TO package.The circuit interconnect includes a dielectric substrate having signaltraces that are electrically coupled to the signal leads. A groundsignal conductor disposed on the dielectric substrate is electricallycoupled with the ground rings.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional objects and features of the invention will be more readilyapparent from the following detailed description and appended claimswhen taken in conjunction with the drawings, in which:

FIG. 1 is a diagram of an optoelectronic assembly in accordance anembodiment of the invention.

FIG. 2 depicts the ground signal conductor side of a circuitinterconnect.

FIGS. 3A and 3B depict the back of a TO package in accordance with thefirst and second embodiments.

FIG. 4 is a diagram of a transmitter assembly in accordance with anembodiment of the invention. FIGS. 4A, 4B, 4C, 4D and 4E are circuitdiagrams of the transmitter assembly of FIG. 4.

FIG. 5 is a diagram of a transmitter assembly in accordance with analternate embodiment of the invention.

FIG. 6 is a diagram of a receiver assembly in accordance with anembodiment of the invention. FIG. 6A is a circuit diagram of thereceiver assembly of FIG. 6.

FIG. 7 is a diagram of a transceiver assembly in accordance with anembodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, there is shown an embodiment of an optoelectronicassembly 100 in accordance with the present invention. Theoptoelectronic assembly may be a transmitter optoelectronic assembly ora receiver optoelectronic assembly. The optoelectronic assembly includesa transistor outline (TO) package 102 that houses an optoelectronicdevice. If the optoelectronic assembly is a transmitter optoelectronicassembly, the optoelectronic device is a light source such as a laserdiode. If the optoelectronic assembly is a receiver optoelectronicassembly, the optoelectronic device is a detector such as a photo diode.

Signal contacts 112, also called signal leads, extend through aperturesin the base 124 of the TO package 102 and contact corresponding signaltraces 114 on a circuit interconnect 104. The signal traces 114 aremechanically and electrically connected to the signal contacts 112 bysolder, conductive epoxy or any other appropriate conductive attachmentmechanism. Signal contacts 112 and signal traces 114 convey power anddata signals between an external circuit 118 and the device or devicesin the TO package 102.

The circuit interconnect 104 is preferably made of an elongated piece offlexible dielectric 120. The dielectric 120 serves as an insulatorbetween a ground signal conductor 116 on one side of the dielectric 120and the data signal traces 114 on the other side of the dielectric. Theground signal conductor 116 conveys ground current between the externalcircuit 118 and the device or devices in the TO package 102. While theembodiment shown in FIG. 1 has two signal contacts 112 and twocorresponding signal traces 114, in other embodiments the number signalcontacts and signal traces may be greater or fewer, depending on thenumber of power and data connections needed by the device or devicesinside the TO package 102.

The external, back surface of the base 124 is sometimes called the“ground plate,” because the base 124 of the TO package is grounded by aconnection between the ground plate and the ground conductor 116 on thecircuit interconnect 104. The ground connection to the base 124 providesa circuit ground voltage source and ground current connection for theelectrical and optoelectronic components in the TO package 102.

To avoid signal reflections and other signal degradations, the impedanceof the signal path from the device in the TO package 102 to the externalcircuit 118 must be kept as consistent as possible. The impedance of thecircuit interconnect 104 (i.e., the characteristic impedance of thetransmission line formed by the circuit interconnect) is preciselydetermined by the thickness of the dielectric and the width of the datasignal traces, and the circuit interconnect is configured so that forfrequencies in the range of 3 to 10 GHz its impedance approximatelymatches the impedances of both the circuitry inside the TO package andthe external circuit 118. As used in this document, two impedances aredefined to “approximately match” when the two impedances are eitherexactly the same or one of the impedances is larger than the other, butno more than 50% larger. In other words, the impedance of the circuitinterconnect is within a factor of about 1.5 of the impedance of thecircuitry inside the TO package and the external circuit 118. Preferablythe impedance of the circuit interconnect will be within 25% (i.e.,within a factor of about 1.25) of the impedances of the circuitry insidethe TO package and the external circuit 118. The impedance of thecircuit interconnect 104 of the present invention is typically between20 and 30 ohms.

In other embodiments, the circuit interconnect 104 may be optimized forimpedance matching (to the high frequency signal leads of the TO package102, and also to an external circuit) for a different range of operatingfrequencies than 3 to 10 GHz. Typically, the range of operatingfrequencies at the circuit interconnect 104 of the present inventionapproximately matches impedances at both ends of the circuitinterconnect 104 will include a range of frequencies above 3 GHz.

In a preferred embodiment the circuit interconnect 104 has a thicknessbetween 0.003 and 0.012 inches, and the dielectric substrate 120 of thecircuit interconnect is preferably polyimide or polyester. Otherinsulating materials may be used besides polyimide or polyester.Moreover, the insulator 120 does not necessarily need to be flexible;however, the flexibility is useful for fitting the optoelectronicassembly 110 into a housing (not shown), such as the housing of anoptoelectronic transmitter, receiver or transceiver. The flexibledielectric substrate 120 is coated on each side with a conductivematerial such as copper, a copper alloy, or other malleable, highlyconductive metal or metal alloy. The data signal traces 114 arefabricated from the conductive material on one side of the circuitinterconnect 104, while the entire second side of the circuitinterconnect 104 (excluding circular regions corresponding to thepositions of the signal leads traversing the base of the TO package)serves as the ground signal conductor 116. Other methods of creating theconductive signal traces may be used as is understood by one skilled inthe art.

In an alternate embodiment, only a portion of the second side of thecircuit interconnect 104 serves as the ground signal conductor 116,leaving room for one or more additional signal traces (e.g., for poweror low frequency data signals) on the second side of the interconnect104. In this alternate embodiment, the ground signal conductor 116 wouldbe positioned relative to the traces on the first side of the circuitinterconnect so as to provide connections with well controlledimpedance.

The side of the circuit interconnect 104 that serves as the groundsignal conductor 116 is depicted in FIG. 2. The small circular regions130 represent holes in the dielectric substrate 120 of the interconnect,through which the signal leads of the TO package extend. The annularcircular regions 132 surrounding the smaller holes 130 representnon-conductive, unmetalized regions in which the conductive material hasbeen removed from the second side of the circuit interconnect 104 so asto prevent electrical shorts between the signal leads and the groundsignal conductor 116.

Returning to FIG. 1, the data signals are transmitted between theoptoelectronic device in the TO package 102 and electrical circuitry118. The data signal contacts 112 extend through apertures in the base124 of the TO package 102 and contact the data signal traces 114. Foreach data signal contact 112, a separate, respective ground ring 106surrounds the data signal contact 112 and is attached to the base 124 ofthe TO package 102. The base 124 is a circular (actually, cylindrical)metal plate, generally held at the circuit ground voltage duringoperation of the optoelectronic device. The base 124 is the foundationof the TO package 102. In a preferred embodiment the base 124 is made ofa metal known as “Alloy 42,” which is an alloy of iron and nickel. Inother embodiments the base 124 may be made of other appropriate metals.The primary purpose of the ground rings is to form a low reflectionconnection between the data signal contacts 112 and the circuitinterconnect 104, so as to minimize signal reflections at the interfacebetween the data signal contacts 112 and the circuit interconnect 104.In some embodiments, ground rings 106 are used only with high frequencydata signal contacts 112 (e.g., carrying data signals at frequencies ator above 2 or 3 GHz), but not with the power signal contact and anylower frequency data signal contacts, because ground rings 106 are notneeded to form low reflection connections between the signal contacts112 and the circuit interconnect 104 for low frequency connections.

FIG. 3A shows the ground rings 106 on the back surface of the base 124.The ground rings 106 are preferably highly conductive, thin metal ringsthat are bonded to the back, planar surface of the base 124, such as bysolder, conductive epoxy or any other appropriate bonding or conductiveattachment mechanism. As a result, the ground rings are mechanically andelectrically connected to the back surface of the base 124. The groundrings 106 rise slightly above the back planar surface of the base 124,which facilitates the bonding of the ground signal conductor 116 of thecircuit interconnect 104 to the ground rings. Alternately, the groundrings 106 may be implemented as raised annular regions of the base 124,i.e., as integral parts of the base. The circuit ground connectionprovided by the ground signal conductor 116, which is electrically andmechanically bonded to the ground rings 106, and possibly other portionsof the base as well, keeps the entire base 124 at the circuit groundvoltage during normal operation. While the ground rings 106 are shown inFIG. 3A as being circular or annular in shape, in other embodimentsother shapes could be used. For instance, the ground rings 106 could beoval shaped structures.

Although there are two ground rings 106 surrounding the two data signalcontacts, only one ground ring is seen in FIG. 1 because of the angle ofthe perspective view shown in FIG. 1. The ground signal conductor 116directly contacts the ground rings 106, and carries ground current fromthe ground rings 106 to a circuit ground terminal 122 (FIG. 1). In apreferred embodiment, the ground signal conductor 116 also directlycontacts the base 124 at the back surface of the TO package 102 so as toprovide a high quality ground connection to the entire TO package andthe devices therein. These contacts between the ground signal conductor116 and the ground rings 106 and the back surface of the base 124 arepreferably implemented by bonding these components together usingsolder, conductive epoxy or any other appropriate bonding or conductiveattachment mechanism.

The ground signal and the data signals are maintained in a closerelationship to each other, separated by the insulator 120. Thisprovides for a controlled impedance at high frequencies.

Referring again to FIG. 1, the electrical circuitry 118 is electricallyconnected to the circuit interconnect 104. The signal traces 114 contactthe electrical circuitry 118 while the ground conductor 116 contacts theelectrical circuitry's circuit ground node 122. The electrical circuitryis typically mounted on or includes a circuit board (not shown) and thecircuit interconnect is electrically connected to that circuit board.The electrical circuitry 118 amplifies and processes the electricalsignals transmitted to a laser diode (in one embodiment) or from a photodiode (in another embodiment), or both (in yet another embodiment).Thus, the electrical circuitry 118 may include a laser driver circuit, areceived signal recovery circuit, or both. Further, the electricalcircuitry 118 may include digital signal processing circuits, such asserializing circuits and deserializing circuits, and circuits thatperform data conversions, such as the 8b/10b conversion for converting adata stream into a “balanced” data stream that is balanced with respectto 1 and 0 bits, and that provides sufficient data transitions foraccurate clock and data recovery.

FIG. 3A shows the base 124 at the back of the TO package 102 in oneembodiment of the present invention. The signal contacts (leads) 112carrying data signals and/or a power supply voltage extend throughapertures in the base 124 of the TO package 102. The data signalcontacts 112 contact the data signal traces 114 (FIG. 1) of the circuitinterconnect. The signal contacts 112 do not contact the base 124 of theTO package 102; rather, they extend through a dielectric 140, preferablya ring of glass, embedded in the base 124. Each dielectric ring 140 isconcentric with one of the signal contacts 112. When the circuitinterconnect 104 is bonded to the base of the TO package 102, theunmetalized insulator region 132 (FIG. 2) on the second side of thecircuit interconnect overlaps the dielectric ring 140 in the base 124.For each data signal contact 112 (or at least each high frequency datasignal contact), there is a conductive ground ring 106 that surroundsthe dielectric 140, concentric with the contact 112 and the dielectricring 140.

In some embodiments, the ground rings 106 are the only parts of the TOpackage that directly contact the ground signal conductor 116 of thecircuit interconnect. In one embodiment, however, the ground signalconductor 116 is mechanically and electrically bonded to a large portionof the external, back surface of the base 124, in addition to the groundrings 106. Alternatively, additional ground contacts may be provided bysignal leads connected to the TO package.

FIG. 3B depicts an alternate embodiment, in which a ground lug 150 isused instead of the ground rings 106 to provide a high quality groundconnection to the base 124 and to prevent signal reflections in the highfrequency data signal paths. The ground lug 150 is a preferably a highlyconductive, thin metal lug bonded to the back, planar surface of thebase 124, such as by solder, conductive epoxy or any other appropriatebonding or conductive attachment mechanism. The ground lug 150 risesabove the back planar surface of the base 124, which facilitates thebonding of the ground signal conductor 116 of the circuit interconnect104 to the ground lug. Alternately, the ground lug 150 may beimplemented as a raised regions of the base 124, i.e., as an integralpart of the base. The ground lug has two round (i.e., cylindrical) holesin it, aligned with the dielectric rings 140 surrounding the data signalcontacts 112.

The use of a ground lug, instead of ground rings, typically does notrequire any change in the design of the circuit interconnect 104. Asshown in FIG. 3B, the ground lug 150 is preferably positioned so as tosurround the data signal contacts 112. If the TO package includes morethan two high frequency data signal contacts 112, either the ground lugmay be made larger or one or more additional ground lugs 150 may bepositioned around those additional signal contacts 112 so as to providea ground current path that is precisely positioned with respect to thedata signal current flowing each of the data signal contacts 112.

The low impedance connection or bond between the ground signal conductorand the ground lug 150 is preferably formed by placing solder on the topsurface of the ground lug or on the back surface of the ground signalconductor 116 and then soldering the ground signal conductor 116 to theground lug 150. Alternately, the ground signal conductor 116 may bemechanically and electrically connected to the ground lug 150 using aconductive epoxy or any other appropriate conductive attachmentmechanism.

In yet another alternate embodiment, the base 124 of a TO package 102may include both ground rings and ground lugs for forming ground currentconnections to the ground signal conductor 116 of the circuitinterconnect 104.

Referring to FIG. 4, there is shown a transmitter optoelectronicassembly 400 in accordance with an embodiment of the present invention.The transmitter optoelectronic assembly 400 includes:

-   -   a laser diode 402, such as an edge emitter or other type of        laser diode;    -   a laser submount 404, on which the laser diode is mounted; the        laser submount 404 may be made of aluminum nitride or alumina        ceramic; the laser submount 404 preferably incorporates one or        more integrated or attached passive components, such as        resistors, capacitors, and inductors, to provide improved        impedance matching and signal conditioning;    -   a laser pedestal 406 to which the submount 404 is attached; the        laser pedestal 406 is a grounded, conductive structure having a        partially concentric shape with respect to data signal contacts        412, 414 that extend through the base 124;    -   a monitor photo diode 408 for detecting the light emitted from a        back facet of the laser diode 402 in order to monitor the        intensity of the light emitted by the laser diode 402;    -   a monitor photo diode sub-mount 410 on which the monitor photo        diode 408 is mounted; and    -   a Transistor Outline (TO) package 420 incorporating controlled        impedance glass-metal feedthroughs.

The partially concentric shape of the pedestal 406, which is held at thecircuit ground potential, facilitates control of the impedancecharacteristics of the circuit that runs from the data signal contacts412, 414, through bond wires 405 to the laser diode 402 and through thelaser submount 404 and laser pedestal 406 of the TO package.

The laser diode 402 is activated when a positive voltage is appliedacross the p-n junction of the laser diode 402. In the preferredembodiment, data signal contacts 412, 414 form a differential datasignal connection. The two contacts 412, 414 are electrically connectedto the laser submount 404 via bond wires 405 or any another appropriateconnection mechanism. One terminal of the laser diode 402 is in directcontact with the laser submount 404 and is therefore electricallyconnected with one of the differential data signal contacts 414 via acorresponding one of the bond wires 405. The other data signal contact412 is electrically connected to the laser diode 402 via a bond wire 405to the submount 404 and another bond wire connecting the second terminalof the laser diode 402 to the submount 404. The differential signalprovided by data signal contacts 412, 414 supplies both a bias voltageand a time varying signal voltage across the p-n junction of the laserdiode 402.

Improved impedance matching between the circuit interconnect and theelectrical circuitry in a TO package is achieved by incorporatingresistors, capacitors and/or inductors into the submount 404 for thelaser diode to provide a network (e.g., an RL network, or LC network, orRLC network) that compensates for the impedance presented by the bondwires 405 between the data signal contacts 412, 414 extending throughthe TO package and the submount connection points. Typically, the bondwires are made of gold and have inductances of 1 to 5 nanoHenries. FIG.4A is a circuit diagram of the circuit in which data signal contacts 412and 414 are connected to the laser diode 402 through the laser submount404. The resistance, capacitance and/or inductance of the submount 404are adjusted so that the impedance of the electrical circuitry insidethe TO package approximately matches the impedance of the circuitinterconnect. FIGS. 4B, 4C, 4D and 4E are circuit diagrams foralternative impedance compensation networks that may be constructed. InFIG. 4B the submount is represented as a single resistor 404-R. In FIG.4C the submount is represented as two resistors, 404-R1 and 404-R2, oneither side of the laser diode 402. In FIG. 4D the submount isrepresented as a capacitor 404-C connected to ground. Finally in FIG. 4Ethe submount is represented as a resistor 404-R and a capacitor 404-C.Typically component values are 10 to 30 ohms (preferably about 20 ohms)for resistor 404-R and 0.6 to 1.0 picofarads (preferably about 0.75picofarads) for capacitor 404-C. The impedance matching provided by thenetwork incorporated into the submount is preferably optimized for apredefined range of operating frequencies, such as 3 GHz to 10 GHz. Thepredefined range of operating frequencies is preferably the same as therange of operating frequencies at which the optoelectronic device isexpected to be used. In the preferred embodiments, the predefined rangeof operating frequencies includes a range of frequencies above 3 GHz.

Referring again to FIG. 4, as is understood by one skilled in the art,when the laser diode 402 is an edge emitter the laser diode 402 emitslight in both the forward direction and the backward direction, fromforward and back facets. The forward direction refers to the directionin which light is transmitted through a window of the TO package, whilethe backward direction refers to the opposite direction. The laserintensity in the backward direction is proportional to the laserintensity in the forward direction. Thus, it is useful to measure theintensity of the laser in the backward direction in order to track thelaser intensity in the forward direction. Accordingly, a monitor photodiode 408 is positioned facing the back facet of the laser diode 402. Apower supply voltage contact 416 is connected to the monitor photo diodesubmount 410 by a bond wire. The monitor photo diode 408 is in contactwith the monitor photo diode submount 410 and is connected to themonitor photo diode data signal contact 418 by a bond wire. Thus, themonitor photo diode 408 is reverse biased between the power supply andthe data signal contact 418. The transmitter assembly of FIG. 4 isoperated in conjunction with a circuit interconnect having four datasignal traces. The circuit interconnect, not shown, is preferablysimilar to the one shown in FIG. 2, but having four data signal traces114. Each data signal trace contacts a respective one of the data signalcontacts 412, 414, 416, and 418.

Other transmitter embodiments may include a Vertical CavitySurface-Emitting Laser (VCSEL) transmitter assembly 500 as shown in FIG.5. The VCSEL 502 is mounted to a submount 504, which is preferably acapacitor. The capacitor is mounted to the TO package 510. The VCSEL iselectrically connected to the submount 504 via direct contact. Contact506 is connected to the submount by a bond wire 505 and contact 508 isconnected to the VCSEL by another bond wire 505. A differential signalis provided through contacts 506 and 508, which results in a positivevoltage across the VCSEL's p-n junction thereby activating the VCSEL502. The transmitter assembly of FIG. 5 is operated in conjunction witha circuit interconnect having two data signal traces, as well as a powerconnection trace, similar to the interconnects shown in FIGS. 1 and 2.Each data signal trace contacts a respective data signal contact 506,508.

Referring to FIG. 6, there is shown an embodiment of a receiveroptoelectronic assembly 600 in accordance with the present invention.The receiver optoelectronic assembly includes:

-   -   a photo diode 602;    -   a photo diode submount 604;    -   an integrated circuit preamplifier 606 attached to the photo        diode 602 and the submount 604;    -   a capacitor 608 for filtering background noise; and    -   a Transistor Outline (TO) package 616 incorporating controlled        impedance glass-metal feedthroughs.

The photo diode submount 604 is preferably a capacitor that serves tofilter noise from the power supply (Vcc) 614. The photo diode 602 iselectrically connected to the submount 604 preferably through directcontact. The photo diode 602 is reverse biased between the chargedcapacitor 608 and a bond wire 605 to the integrated circuit preamplifier606. The integrated circuit preamplifier 606 produces a pair ofdifferential data signals through bond wires 605 to contacts 610 and612. Finally, as is understood by those skilled in the art, thecapacitor 608 is used by the integrated circuit preamplifier 606 tofilter unwanted noise from the data signals. The receiver optoelectronicassembly of FIG. 6 is operated in conjunction with a circuitinterconnect having three data signal traces (not shown, but similar tothe circuit interconnects shown in FIGS. 1 and 2). Each data signaltrace contacts a respective one of the data signal contacts 610, 612,and 614. The data signals from the photo diode are typically transmittedthrough the circuit interconnect to a received signal amplifier that ismounted on the circuit board connected to the circuit interconnect.

FIG. 6A is a circuit diagram of the receiver assembly shown in FIG. 6.The photo diode 602 is reverse biased so that V2 is less than V1. Theoutput from the photo diode is amplified by the integrated circuitpreamplifier 606 and then output through the data signal contacts 610and 612. The photo diode submount is represented as a capacitor 604 thatfilters noise from the power supply (Vcc) 614. The capacitor 608 filtersnoise from the data signals.

FIG. 7 shows an embodiment of an optoelectronic transceiver 700 inaccordance with the present invention. The optoelectronic transceiver700 includes a transmitter TO package 702 and receiver TO package 704.The transmitter TO package 702 houses a light source such as a laserdiode, and the receiver TO package 704 houses a detector such as a photodiode. Data signals are transmitted from external electrical circuitry710 to the transmitter TO package 702 via the transmitter circuitinterconnect 706. The data signals from the detector are transmittedthrough the receiver TO package 704 to the external electrical circuitry710 via the receiver circuit interconnect 708. Both the transmittercircuit interconnect 706 and the receiver circuit interconnect 708ground their respective TO package through direct contact with theground rings 712 (two of which are shown in FIG. 7) surrounding the datasignal contacts 714.

While the present invention has been described with reference to a fewspecific embodiments, the description is illustrative of the inventionand is not to be construed as limiting the invention. Variousmodifications may occur to those skilled in the art without departingfrom the true spirit and scope of the invention as defined by theappended claims.

1. An optoelectronic assembly, comprising: a transistor outline (TO)package, including: a base; a plurality of leads passing through thebase; and a plurality of ground rings, each of which is disposed about acorresponding lead and is electrically coupled with the base, and eachground ring being electrically isolated from the respectivecorresponding lead; an optoelectronic device disposed in the TO packageand electrically coupled with at least one lead; a circuit interconnectelectrically coupled to the optoelectronic device and the TO package,the circuit interconnect comprising: a dielectric substrate; a pluralityof signal traces disposed on the dielectric substrate, each of thesignal traces being electrically coupled with a corresponding lead ofthe TO package; and a ground signal conductor disposed on the dielectricsubstrate and electrically coupled with the ground rings.
 2. Theoptoelectronic assembly as recited in claim 1, wherein the plurality ofleads includes a power lead and a signal lead.
 3. The optoelectronicassembly as recited in claim 1, wherein the plurality of leads includesa plurality of signal leads, each of which has one of the ground ringsdisposed thereabout.
 4. The optoelectronic assembly as recited in claim1, wherein the optoelectronic device comprises one of: a detector; and,a light source.
 5. The optoelectronic assembly as recited in claim 1,wherein the dielectric substrate substantially comprises a flexiblematerial.
 6. The optoelectronic assembly as recited in claim 1, whereinthe circuit interconnect defines a plurality of openings, each of whichreceives a corresponding lead of the TO package, the leads beingelectrically isolated from the ground signal conductor of the circuitinterconnect.
 7. The optoelectronic assembly as recited in claim 1,wherein each lead of the TO package physically contacts a correspondingsignal trace.
 8. The optoelectronic assembly as recited in claim 1,wherein the plurality of ground rings comprise respective raised annularregions of the base.
 9. The optoelectronic assembly as recited in claim1, further comprising electrical circuitry electrically coupled with theplurality of signal traces, and the electrical circuitry including aground node to which the ground signal conductor is electricallycoupled.
 10. The optoelectronic assembly as recited in claim 9, whereinan impedance of the circuit interconnect is within a factor of about1.25 to about 1.5 of: an impedance associated with the TO package; and,an impedance of the electrical circuitry.
 11. An optoelectronicassembly, comprising: a transistor outline (TO) package, including: abase; a plurality of leads passing through the base; and a plurality ofground rings, each of which is disposed about a corresponding lead andis electrically coupled with the base; a dielectric interposed betweeneach ground ring and corresponding lead; an optoelectronic devicedisposed in the TO package and electrically coupled with a plurality ofleads; a circuit interconnect electrically coupled to the optoelectronicdevice and the TO package, the circuit interconnect comprising: adielectric substrate; a plurality of signal traces disposed on thedielectric substrate, each of the signal traces being electricallycoupled with a corresponding lead of the TO package; and a ground signalconductor disposed on the dielectric substrate and electrically coupledwith the ground rings; and electrical circuitry electrically coupledwith the plurality of signal traces, and the electrical circuitryincluding a ground node to which the ground signal conductor iselectrically coupled.
 12. The optoelectronic assembly as recited inclaim 11, wherein the plurality of leads includes a power lead and asignal lead.
 13. The optoelectronic assembly as recited in claim 11,wherein the plurality of leads includes a plurality of signal leads,each of which has one of the ground rings disposed thereabout.
 14. Theoptoelectronic assembly as recited in claim 11, wherein theoptoelectronic device comprises one of: a detector; and, an opticaltransmitter.
 15. The optoelectronic assembly as recited in claim 11,wherein the dielectric substrate substantially comprises one of:polyimide; or, polyester.
 16. The optoelectronic assembly as recited inclaim 11, wherein the dielectrics disposed about the signal leadssubstantially comprise glass.
 17. The optoelectronic assembly as recitedin claim 11 wherein, for leads about which both a ground ring anddielectric are disposed, the dielectric is interposed between the leadand the ground ring.
 18. The optoelectronic assembly as recited in claim11, wherein the ground signal conductor physically contacts the base ofthe TO package.
 19. The optoelectronic assembly as recited in claim 11,wherein at least one of the plurality of signal traces is disposed on aside of the dielectric substrate opposite a side of the dielectricsubstrate upon which the ground signal conductor is disposed.
 20. Theoptoelectronic assembly as recited in claim 11, wherein the circuitinterconnect defines a plurality of openings, each of which receives acorresponding lead of the TO package, the leads being electricallyisolated from the ground signal conductor of the circuit interconnect.21. The optoelectronic assembly as recited in claim 11, wherein eachlead of the TO package physically contacts a corresponding signal trace.22. The optoelectronic assembly as recited in claim 11, wherein animpedance of the circuit interconnect is within a factor of about 1.25to about 1.5 of: an impedance associated with the TO package; and, animpedance of the electrical circuitry.